Memory modules comprise a multiplicity of electronic components and circuits, typically integrated into an integrated circuit (IC). Electric components in general and semiconductors in particular change their behavior in response to changing operating conditions, e.g., changing temperature, supply voltage level and so on.
The ever increasing package density of ICs increases this effect even further, with individual structures of a semiconductor being pushed closer to physical boundaries. In parallel, the voltage levels decrease in order to save power. This often results in a poor signal-to-noise ratio.
At the same time, the use of electronic devices in mobile environments makes it harder to control the operating conditions under which the electronic devices are used. Battery powered devices are subject to changing supply voltage levels as batteries are charged and discharged.
Devices used outdoors can experience big changes in operating temperature, pressure or humidity. Users expect their mobile devices to cope with such changes. Consequently, the demand for electronic components, which are independent of such changing operating conditions, rises.
This problem is particularly relevant for memory modules, as they exhibit a very high package density and are operated at very low supply voltages, e.g., down to 1.8 V. Because of their mechanical robustness, semiconductor memory modules are used in many portable devices, e.g., as built-in storage of personal media players or on exchangeable memory cards used for digital cameras.
It is known to adapt individual circuit components of a memory module. For example, the time used to sense the state of a memory cell can be increased for memory modules designed to operate at a low supply voltage level. This is useful in a circuit where a bit line of a memory cell is discharged over a sense amplifier. Since the supply voltage and consequently the gate voltage used to enable the discharge path are relatively low, e.g., in comparison with a memory module operated with a higher supply voltage, the discharge process will take longer.
A timing circuit used to control the sense amplifier could be trimmed, for example, by adding or removing elements of a delay chain. However, since different electronic circuits of a memory module react differently to changing operating conditions, each circuit component is adapted individually. This often leads to complex designs comprising redundant solutions, costing valuable design time and chip area. As a consequence not all the electronic components can be adapted to operating conditions.
Consequently, there exists a need for memory modules or for other circuitry in general with a simple circuit design, which can be used in a wide range of operating conditions.